1. Technical Field
The present invention relates to methods and system for generating captions over three-dimensional (3D) images.
2. Background
FIG. 1 schematically illustrates display of a caption 10 over a two-dimensional (2D) image 12 included as part of a television program showing within a television screen 14. The illustration depicts a situation in which the caption 10 may be used to provide a textual description of a dialogue or other audio taking place within the television program. The caption 10 is shown to be at the side of the image 12 for exemplary purposes. The caption 10 may be directly over the image 12 to prevent viewing of the covered portion of the image 12. This process is commonly referred to as closed captioning when the caption 10 is used to textually describe audio events taking placing within the television program. The particular positioning of the caption 10 within the television screen 14 may be defined according to an x-axis and y-axis of the screen 14 in which the caption 10 is to appear, i.e., x and y values may be used represent a placement location of the caption 10 respectively within the x-axis and y-axis of the screen 14, such as the placement defined according to ANSI-CEA-708, which is hereby incorporated in its entirety. The caption 10 is then added to the video frames used to render the image 12 at the location specified with the 2D coordinates. This type of 2D placement coordinate may work well for placing the caption 10 relative to 2D images but is problematic when used to place the caption 10 near 3D images.
The rendering of 3D images is typically accomplished in a stereoscopic manner by rendering separate left and right viewpoint images such that the images from each viewpoint appear independently to each eye as a 3D object. Since a caption 10 added according to the 2D coordinate system will be added to part of the left viewpoint portion of the frame and part of the right viewpoint image of the frame, the 3D television displays the left and right viewpoint images independently such that only the portion of the caption 10 within each viewpoint is displayed at the same time. This essentially creates a 3D image that overlaps the two portions, rendering the closed caption text illegible.